The class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon is known in the art. An early production of such polymers is disclosed by Nozaki. See, for example, U.S. Pat. No. 3,694,412. More recent processes for the production of such linear alternating polymers are disclosed in a number of published European Patent Applications including 121,965, 181,014, 213,671 and 257,663. In general, the latter processes employ a preferred catalyst composition formed from a compound of palladium, a strong non-hydrohalogenic acid having a pKa below 2 and a bidentate ligand of phosphorus or nitrogen. The polymeric product is typically of a structure represented by the repeating formula ##STR1## wherein A is the moiety of at least one ethylenically unsaturated hydrocarbon polymerized through the ethylenic unsaturation.
When the ethylenically unsaturated hydrocarbon to be polymerized is cyclic in structure, particularly polycyclic in structure, it is often advantageous to use a catalyst composition wherein the bidentate ligand is a bidentate ligand of nitrogen. In U.S. Pat. No. 4,788,279 there is disclosed a process for the production of linear alternating polymers of carbon monoxide and norbornene or dicyclopentadiene. The production of linear alternating polymers of carbon monoxide and substituted norbornene compounds is described in copending U.S. patent application Ser. No. 379,839, filed Jul. 14, 1989. The type of polymer product resulting from such polymerizations will vary, however, with the type of ethylenically unsaturated cyclic hydrocarbon.
In the case of polymers of carbon monoxide and norbornene compounds which are produced according to the above procedures, typically employing reaction temperatures above 60.degree. C. and relatively high ratios of bidentate ligand to acid anion in the catalyst composition, the structure of the polymers is generally in accord with the above formula I. In the case of the polymers of carbon monoxide and dicyclopentadiene, however, the polymers are linear and alternating but have a structure in which the moieties originating from carbon monoxide are predominantly in a spiroketal structure of the general formula ##STR2## wherein Z represents the remainder of the dicyclopentadiene molecule other than the two carbon atoms of the ethylenic unsaturation in the 5- and 6-ring positions. The monoolefinic materials such as norbornene or 2,3-di-substituted norbornene will have less than about 25% of the moieties originating from carbon monoxide in the spiroketal structure of formula II and more than about 75% in the ketone structure of formula I. The diolefinic compounds such as dicyclopentadiene form linear alternating polymers with carbon monoxide in which more than 75% of the moieties originating from carbon monoxide are of the spiroketal structure represented by formula II. For some purposes it may be desirable to have a linear alternating polymer of carbon monoxide and a norbornene compound of the nature of formula II with a high proportion of spiroketal units. It would therefore be of advantage to provide a process for the production of linear alternating polymers of carbon monoxide and norbornene compounds in which a higher proportion of the moieties originating or derived from the carbon monoxide are in a spiroketal structure.